Now I am at a loss (hope it's not early old-timers disease).
To answer your question, this project was started in AC15 using Eric's AMT. The only other relevant info is that I have been using the MasterScript Total Zone as well as other Cadimage add-ons unrelated to this zone issue.
Per your suggestion I have New & Reset All using the default AC template, created rooms with zones using Zone Identifier 2 15, and a zone schedule. Neither the room number or name can be changed for any zone listed in the zone schedule. All layers are visible and unlocked.
AC27 v. 4060 w/ MEP, Cadimage, Twinmotion 2023.2.2 using AC from AC6.0, 2021 MacPro M1 chip, Adobe CC. Used AC on both platforms.